A vehicle such as a motorcycle, an automobile or a truck uses a plurality of lights mounted externally on the vehicle to indicate certain information about the vehicle to other drivers and pedestrians. Typically, such lights are mounted on the rear end of the vehicle on both left and right sides of the vehicle's rear end.
A brake light is used to inform others that the driver has applied the brake and is thus beginning to slow down the vehicle. A tail light is used at night to indicate the presence of the vehicle to others. Indicator lights are used to inform others that the driver has signalled his/her intention to turn the vehicle either left or right, depending on which indicator light is turned on.
In the prior art, separate single filament lighting bulbs were used for all three of these functions. Alternatively, the brake and tail light functions were combined in a single two-filament bulb, with one filament dedicated to the brake light function and the other filament dedicated to the tail light function. Each filament requires a separate wire to energize the filament. Therefore, for the prior art systems mentioned above a total of six wires is required to energize the lighting system.
This leads to a complicated wiring scheme involving many wires. The more wires involved, the higher the chance that a wire defect will occur. Also, the connection of the lighting system is made more complicated by an increased number of wires. The more wires involved, the more space for laying wiring must be provided. In smaller vehicles such as a motorcycle, such space is critical. Further, with a motorcycle, drivers often like to custom design their vehicle, and thus a complicated wiring system involving many wires makes designing the vehicle quite difficult.
Another problem with the above-mentioned prior art is that with the first prior art version, many bulbs are required (two for each lighting function, since both the left and right sides must be accounted for). This makes it difficult to reduce the size of the overall lighting package, a goal which is especially important in smaller vehicles such as motorcycles.
For the second prior art version, although less overall bulbs are required, complex double filament bulbs must be used. This makes production of the lighting assembly more expensive. Also, this version still requires four bulbs total, and thus also suffers from the problem mentioned above for the first version, although to a lesser extent.
U.S. Pat. No. 5,241,241 discloses a circuit for driving a single bulb (for each of right and left sides) used for both brake and indicator operations. However, this arrangement requires that a separate bulb be provided for the tail light for each side of the vehicle.